Air pressure control for casting cores



Feb. 28, 1967 c. BABER AIR PRESSURE CONTROL FOR CASTING GORES Filed Feb. 15, 1965 Y NM, T Wu Qmvmm 9n 1 w/ W a 3% M a, a. K wv KI Mn. 6 L hh y T @QN om 5% M j X a a m y O Q fi Q R Q NM ww wm m W QW mm MN b Q,

I!!! I r MN United States Patent 3,306,568 AIR PRESSURE CONTROL FOR CASTING CORES Claude Baber, Kettering, Ohio, assignor to The Flexicore Co., Inc, Dayton, Ohio, a corporation of New York Filed Feb. 15, 1965, Ser. No. 432,555 4 Claims. (Cl. 24965) This invention relates to an air pressure control for casting cores and particularly for cores used in casting concrete slabs. Such slabs come in lengths ranging up to as much as 40 feet and are provided with one or more longitudinal passages therethrough. The passages are created by inflatable cores disposed in a casting form during the casting process. Such cores are inflated to a predetermined pressure and after a casting has been cured, such cores are deflated and then withdrawn from the casting.

As a rule, when a core is inflated, it has a cylindrical shape and a diameter of about four inches or six inches, or any other figure, depending upon the size of the slab being cast. The core length is equal to or greater than the slab length. The core material is customarily of a heavy rubberized or plasticised fabric. Like any elastic material, any change in its elastic properties will result in a change of core response to inflation pressure. Such factors as age of the core, ambient temperature have an appreciable effect on core dimensional response to inflation pressure. Thus as an example, elasticity of many cores increases with a rise in ambient temperature. This can cause an increase in core diameter during curing of the slab at an elevated temperature for a number of hours.

Thus in the practical manufacture of slabs, an inflated core is positioned within a casting form so that it will stay put when the casting form is filled with concrete mix and thereafter cured. The curing itself is generally accomplished in a steam room at an elevated temperature of the order of about 150 F. for a period of seven or eight hours, or longer. This temperature, together with the heat generated in the concrete resulting from the hydration of the cement, increases the temperature of the air about and within the core. The action of this temperature rise on the core material results in an increase of the transverse dimension of the core--the actual effect will vary depending upon the age and elasticity of the core material. This transverse enlargement of the core occurs when the concrete has little strength and results in a crack or cracks extending from the core exterior to the bottom or top surfaces of the casting or both. Such a crack renders the product unusable and represents a complete waste of concrete, not to mention the cost of fabrication.

Various attempts to solve this problem have been made. These attempts have been generally unsuccessful and have not taken account of the conditions under which such slabs are manufactured. As a rule, such slabs are manufactured in large buildings where there is considerable dirt and dust. In addition, the employees manufacturing the slab can not be counted upon to take any delicate steps or procedures. This is because the workmen must carry on their duties under surroundings with considerable noise and where the ambient temperature may be decidedly above or below a comfortable room temperature of about 70 F.

This invention provides a construction whereby the air pressure within a core will not increase during casting and may indeed decrease. The invention generally contemplates a valve structure in a core for inflating or deflating the core with air and the provision of a supplementary air bleed passage for permitting a tiny amount of air to leak out into atmosphere during the time that the concrete is curing. The provision of supplementary pas- 3,306,568 Patented Feb. 28, 196'? sage adjacent an air valve structure is particularly effective in regard to the cleaning act-ion of the air on the supplementary passage.

The construction contemplates a generally conventional valve structure readily available in the market but provided with a predetermined auxiliary bleed passageway parallel to the valve for the purpose of permitting air to leak out during the time that the core is inflated and is disposed within -a casting during the curing process. By accurately predetermining the dimensions of the bleed passage, it is possible to have the drop in pressure of the air within the core due to air leakage generally compensate for any tendency of the core to increase its diameter during curing.

The provision of a separate passageway for a slOW air leak adjacent the main air valve is advantageous for a number of reasons. Thus when the air is escaping, there will be a tendency for the air to blow out any dirt. When the tube is being inflated, the compressed air sent into the tube through the valve also flown through the bleed passage and tends to blow any dirt which may have collected. There is thus a tendency for air to flow first in one direction and then in another through the bleed passage in the normal use of the core in connection with the casting operation.

Another advantage of this construction resides in the fact that a standard readily available valve structure may be used. Such valve structures are made to a high degree of accuracy and easily provide good sealing against substantial values of air pressure. Any attempt to introduce a slow leak by adjusting such a valve would be diflicult and costly and could not be relied upon to maintain its characteristics.

A constructon embodying the invention is also readily adapted for use where an inflated form is not put into a casting form immediately after inflation. In such case, a cap or cover for the valve and bleed passage is easily provided as part of a standard valve fitting. The bleed passage itself is obtained in a simple manner by a drilling operation and is susceptible to accurate control.

The invention will now be described in connection with the drawings, wherein:

FIGURE 1 is a view partly in section and with certain parts broken away illustrating a tube having an air valve fitting at one end thereof, the air valve fitting embodying the present invention, but the scale of the drawing making it impossible to show the details clearly;

FIGURE 2 is a view on an enlarged scale of a longitudinal section of a fitting including an air valve embodying the presentinvention;

FIGURE 3 is an enlarged sectional detail on line 33 of FIGURE 2; and

FIGURE 4 is a detail on a still larger scale on line 4-4 of FIGURE 3.

Referring first to FIGURE 1, core 10 of any desired construction is shown. Core 10 may have any desired length suitable for casting slabs and may range up to a length of 40 or 45 feet. The core is flexible and elastic and when inflated is generally cylindrical in shape. As a rule, such cores have a comparatively small transverse dimension, a common diameter, for example, being about four inches in some instances or six inches in other instances. However, the diameter depends upon the size of slab being cast and the invention is not limited in any way to any physical dimensions of the core. Core 10 consists of a tubular member 12 which may be of rubberized material and may include a combination of rubber and cotton or nylon such as, for example, is disclosed in Patent No. 3,104,441. Core 10 has dead end member 14 which may be formed of plastic, metal or the like. Core material 12 is clamped over end mem- 3 her 14 by bands 15 and 16 of any suitable material, metal or non-metal. The dead end of the core is airtight.

The live end of the core, generally indicated by 21), consists of body 21 tightly secured to the flexible core material by bands 22 and 23 in a manner generally similar to the dead end. Live end of the core includes handle 26 of steel or any other material for pulling the core. Body 20 of the dead end has fitting 30 secured therein as by threading. No attempt is made to show the relative dimensions of fitting 3t) and the core proper. Fitting 30, however, may be a commercially available fitting having a suitable valve permitting connection to a compressed air hose to inflate the core.

Since the invention is primarily concerned with fitting 30, and since the core and the remainder of the core structure is conventional, the fitting, as an example of a suitable structure, will now be described in detail.

Referring specifically to FIGURES 2 to 4 inclusive, fitting 30 is of metal or other material and includes body portion 31 having chamber 32 therein. Chamber 32 is provided with shoulder 33 against which spider 34 can rest. Spider 34 has the central portion thereof apertured at 35 and supports one end of valve bias helical spring 36. The other end of valve bias spring 36 is disposed around reduced end 39 of valve stem 40. Valve stem 40 includes tapered valve plate member 42 which cooperates with O-ring 43 of rubber or other gasket material for providing a valve action.

O-ring 43 is disposed within annular groove 45 of rigid housing member 46. Housing member 46 has internally threaded portion 47 which cooperates with externally threaded portion 48 of body portion 31. Housing member 46 and body portion 31 are rendered airtight by O-ring 50 between the two, as illustrated. Housing portion 46 has nipple portion 53 having bore 54 of cylindrical shape within which valve stem 40 can move longitudinally. Spring 36 normally biases the valve to a closed position as illustrated. However, air in nipple 53 at a pressure suificient to overcome the bias due to spring 36 will open the valve and permit air to flow through bore 54 past tapered valve 42 into the interior of the valve body.

The construction so far described is conventional and is available on the market. The particular structure disclosed has the outside surface of nipple 53 suitably shaped to permit snap locking or unlocking of a cooperating female fitting. The female fitting illustrated in FIGURE 2 for cooperation with fitting 30 is a cap for closing the valve. It is understood, however, that the female fitting may just as well be attached to the end of an air hose for supplying air to open the valve. The female fitting is in two parts and consists of longitudinally slidable sleeve 57 and female fitting proper 60.

It is female fitting 60 which is shown as a cap but which can be apertured and attached to the end of an air hose as desired. Sleeve 57 is movable to permit locking or unlocking of the female fitting. Sleeve 57 is normally biased at the position shown by coil spring 61 extending between shoulder 63 of female fitting 6t) and internal shoulder 64 of sleeve 57. Sleeve 57 is in the position shown due to coil spring 61 and is limited in its travel by O-ring 66 disposed in a groove about end 68 of female fitting 60. The locking action is obtained by a number of small balls 70 of steel or other rigid material disposed at spaced intervals about nipple 53 and located in recess 72 in this nipple. In practice, there may be two or three such balls 70. Gasket 73 in section has a V shape and is disposed around the end of nipple 53 and normally lies within and is carried by the inside of female fitting 60.

In order to remove female fitting 60 from fitting 30, it is necessary to move sleeve 57 to the right as seen in FIGURE 2, this being against the bias of spring 61. When sleeve 57 is moved to the right sufficiently, en-

larged inside surface 76 will be opposite balls and will permit these balls to move outwardly out of recesses 72. This will permit female fitting 60 to be pulled free from the grooved portion of nipple 53, the female fitting carrying sleeve 57 with it. As soon as sleeve 57 is re leased, it assumes its normal bias position but balls 70 are now free of nipple 53.

Balls 70 are prevented from falling out by the locking action of the portion of the fitting retaining these balls. The particular valve structure and fitting so far described is available on the market and is manufactured and sold by Suap-Tite Company of Union City, Pennsylvania. This company has various fittings and sizes available. Other companies have generally similar valve structures wherein a locking fitting can be used with a valve. It is not necessary for the invention that the fitting be of the locking type. Any valve structure having a plate valve member may be used. Referring now in detail to valve member 42, it will be understood that this member is of rigid material and will usually be of steel or other metal, although a strong plastic may also be used.

Referring in particular to FIGURES 3 and 4 and in accordance with the invention, tapered valve member 42 has a plate portion which functions as a barrier between the high and low pressure sides of the valve. Thus, for example, valve stem 40 in this instance has three flutes 40a and a central rod-like stem 40]) and leaves a considerable area of the valve plate member as a wall dividing the low and high pressure regions. In this plate portion of the valve and in accordance with the present invention, there is provided bleed passage 80. Passage 80 may be most easily formed by providing recess 81 of a size that can be readily handled by ordinary drill bits and then passage 80 itself may be drilled accurately to a fine diameter for a prescribed length.

Thus as an example, recess 81 may have a diameter of about 2" or These diameters are readily obtainable with bits that can handle metal or plastic. Passage 80 will have a much smaller diameter and may be of the order of between about three or four mils (.003 or .004 inch) in diameter to as much as about .010 inch. The diameter will depend upon the desired leakage characteristics and relative lengths of large and small passages. It is possible to drill fine holes in metal or plastic with bits that are available on the market. However, it is preferred to reduce the amount of such fine drilling to a minimum. Accordingly, larger passageway 81 is provided to reduce the amount of drilling necessary. It is evident that increasing the length of fine passage 80 will permit the diameter of this passageway to be increased to obtain the same bleed action. It is preferred to have the length of such a passageway reduced to minimize the chances of clogging the same.

The dimensions of the two passages both as regards length and diameter for a particular core size can be predetermined and after such determination can be utilized to obtain desired bleeding effects. It is clear that when a core is being inflated, compressed air will not only go to the main valve opening in the valve structure, but will also pass through bleed passage 80. After the tube has been inflated, air within the tube will leak through bleed passage 80 while the valve is closed. It is understood that when the core is being used in connection with casting, no attempt will be made to seal the valve as a whole, such as illustrated, for example, in FIGURE 2. It is possible to provide a cap fitting such as illustrated in FIGURE 2, wherein air leaking through passage 80, after the core has been inflated, can also leak through the cap. This would minimize access of sand and dirt to the entire valve, although this wound generally not be necessary since the flow of air through bleed passage 80 would tend to keep this passage clean. An air-tight cap such as is illustrated in FIGURE 2 is useful when a core has been inflated and is to be kept in this condition for a number of hours before use. As a rule, however,

such a cap need not be used, since the core is used promptly after inflation. In general, fitting 60 and its sleeve would be left off.

As may be readily appreciated, any valve structure may be used wherein a bleed passage across the valve proper can be provided. Thus during inflation, air will go through fine passage 80 in one direction and after the tube has been inflated, and the air hose disconnected from the valve stem, then air through passage 80 will leak out in reverse direction. Thus, as has been previously pointed out, the entire valve structure will tend to maintain itself clean and free of dirt. This is particularly true if recess 81 is on the core side of the valve member. This is in marked contrast to locating a bleed passage in any other portion of the core. Such other locations would not expose the bleed passage to the cleansing action of air during inflation. Such other locations tend to promote clogging of the passage even though it might appear that such locations with air always going out would keep the bleed passage clean. A further advantage of having the bleed passage within the valve body is that the bleed passage itself is protected and housed by a tubular length of valve body material. Thus, even if the valve structure is not provided with a cap, there will be little, if any, chance for any dirt to get into the fine passage. It should be borne in mind that a bleed passage of the order of several mils can easily become clogged completely or partially and result in a drastic change in the operating characteristics of the core. The invention may be applied to a large variety of valve structures and provides an exceedingly simple and practical solution to a problem which has plagued the industry for many years.

What is claimed is:

1. An inflatable core for use in the manufacture of concrete slabs, said core including an elongated inflatable tube, means at both ends of said tube for rendering said tube airtight, at least one end of said tube having a normally closed air valve for passing air to inflate said tube, said valve being movable in an open position for deflating said core, said valve including a rigid housing having a valve member and valve seat within said housing to divide the interior into low and high pressure regions on opposite sides of said valve member and means within said housing providing a fine air passage in parallel to said valve for bleeding air through said valve when said tube is inflated, the dimensions of said fine air passage predetermined to permit air leakage to generally compensate for any tendency of the core to increase in its diameter during curing.

2. The construction according to claim 1, wherein said valve member has a plate-like portion forming a barrier between the high and low pressure regions when said valve is closed, and said valve member having a fine bleed passage therethrough.

3. The construction according to claim 2, wherein said bleed passage has a diameter of the order of between about three mils and about .010 mils.

4. The construction according to claim 3, wherein said valve has a stern, a nipple around said stern which functions to shield the valve member from the outside, said valve being adapted to pass air under pressure against the normally closed valve to inflate the core, the location of said fine passage providing a cleaning action whether air passes into the core or bleeds outwardly therefrom.

References Cited by the Examiner UNITED STATES PATENTS 950,263 2/1910 Harpster 251117 3,104,441 9/1963 Smith 249 X 3,257,690 6/1966 Scott 249-65 X J. SPENCER OVERHOLSER, Primary Examiner. 

1. AN INFLATABLE CORE FOR USE IN THE MANUFACTURE OF CONCRETE SLABS, SAID CORE INCLUDING AN ELONGATED INFLATABLE TUBE, MEANS AT BOTH ENDS OF SAID TUBE FOR RENDERING SAID TUBE AIRTIGHT, AT LEAST ONE END OF SAID TUBE HAVING A NORMALLY CLOSED AIR VALVE FOR PASSING AIR TO INFLATE SAID TUBE, SAID VALVE BEING MOVABLE IN AN OPEN POSITION FOR DEFLATING SAID CORE, SAID VALVE INCLUDING A RIGID HOUSING HAVING A VALVE MEMBER AND VALVE SEAT WITHIN SAID HOUSING TO DIVIDE THE INTERIOR INTO LOW AND HIGH PRESSURE REGIONS ON OPPOSITE SIDES OF SAID VALVE MEMBER AND MEANS WITHIN SAID HOUSING PROVIDING A FINE AIR PASSAGE IN PARALLEL TO SAID VALVE FOR BLEEDING AIR THROUGH SAID VALVE WHEN SAID TUBE IS INFLATED, THE DIMENSIONS OF SAID FINE AIR PASSAGE PREDETERMINED TO PERMIT AIR LEAKAGE TO GENERALLY COMPENSATE FOR ANY TENDENCY OF THE CORE TO INCREASE IN ITS DIAMETER DURING CURING. 